In the telecommunications industry, modular plug type connectors are commonly used to connect customer premise equipment (CPE), such as telephones or computers, to a jack in another piece of CPE, such as a modem, or in a wall terminal block. These modular plugs terminate essentially two types of cable or cordage: ribbon type cables and standard round or sheathed cables.
In ribbon type cables, the conductors running therethrough are arranged substantially in a plane and run, substantially parallel, alongside each other throughout the length of the cable. The individual conductors may have their own insulation or may be isolated from one another by channels defined in the jacket of the ribbon cable itself, with the ribbon cable providing the necessary insulation. Conversely, the conductors packaged in a standard round cable may take on a random or intended arrangement with conductors of conductor pairs being twisted or wrapped around one another and with the pairs changing relative positions throughout the cable length.
Most modular plugs are well suited for terminating ribbon type cables. Typically, these plugs are of a dielectric, such as plastic, structure in which a set of terminals are mounted side by side in a set of troughs or channels in the plug body such that the terminals match the configuration of the conductors in the cable connected thereto. When the plug is inserted into a jack, the terminals will electrically engage jack springs inside the jack to complete the connection.
A common problem found in these modular plugs is for the conductors to pull away or be pulled away from the terminals inside the plug structure. This can be caused by persons accidentally pulling on the cable, improperly removing the plug from a jack or merely from frequent use. The stress on the connections between the conductors and the plug terminals has been alleviated in prior art devices which include an anchoring member or anchor bar in the housing of the dielectric structure. In these designs, the dielectric structure, i.e., the plug, contains a chamber for receiving the cable. The cable is then secured within the chamber via pressure exerted upon the cable jacket by the anchoring member or anchor bar in conjunction with one or more of the chamber walls. U.S. Pat. Nos. 5,186,649 and 4,002,392 to Fortner et al. and Hardesty contain examples of such strain relief apparatus.
While these modular plugs with anchor bars have been effective in providing strain relief to ribbon type cables, standard round cables or cords pose additional strain relief problems. In U.S. patent application Ser. No. 08/922,621 of Chapman et al., filed Sep. 3, 1997, the disclosure of which is incorporated herein by reference, a plug for terminating a round cable has an anchor bar for holding the cable. While an anchor bar does function to secure the cable, it deforms the cable or cord and presses the individual leads together randomly. As a consequence there is introduced a random variable in performance of the plug as a result of increased cross talk among the conductors or leads, which can vary from cable to cable depending on the cut, and which, as a consequence, makes it difficult to predict a plug's electrical characteristics. The high degree of variability can also result in reduced signal carrying performance.
This process of terminating a round cable introduces significant variability in connecting the conductors to the plug terminals and places additional strain on the connections between the conductors and the plug terminals. Because the individual conductors in a conductor pair are often twisted around one another and the conductor pairs themselves are often twisted around one another, the conductor configuration a technician sees when the cable is cut prior to terminating changes based on the longitudinal position of the cut in the cable. The technician generally is forced to translate the conductor configuration into a side by side orientation matching the pattern of the terminals in the plug. Moreover, the necessity of splitting the conductors in at least one of the pairs, which is an industry standard, presents another potential for error in making the connections to the plug terminals. In addition, orienting the conductor positions from an essentially circular arrangement into a planar arrangement places additional stress on the conductor-terminal connections.
U.S. Pat. No. 5,496,196 to Winfried Schachtebeck discloses a cable connector in which the connector terminals are arranged in a circular pattern to match more closely the arrangement of conductors held in a round cable. However, the Schachtebeck invention attempts to isolate each individual conductor and apparently requires all conductor pairs to be split before termination to the connector.
In addition, the economic aspects of the prior art necessity for the installer to separate out the twisted pairs of conductors and route them to their proper terminals in the plug are of considerable moment. Even if the installer, splicer, or other operator is accurate in the disposition of the conductors, the time consumed by him or her in achieving such accuracy is considerable. Thus, in a single work day, the time spent in properly routing the conductors can add up to a large amount of time, hence money. Where it is appreciated that thousands of such connections are made daily, involving at least hundreds of installers, it can also be appreciated that any reduction in time spent in mounting the plug can be of considerable economic importance.
The plug should demonstrate predictable characteristics, including a minimization of any variation in signal transmission. Thus, the cable should be anchored to the plug in simple, economically viable construction readily adaptable for use in the field.